Multi-antenna (MIMO: Multiple in Multiple out) wireless transmission technology configures multiple antennas at transmit side and receive side and makes use of space resources in the wireless transmission so as to obtain spatial multiplexing gain and space diversity gain. Information theory research shows that MIMO system capacity linearly increases with the minimum value of the number of transmit antennas and the number of receive antennas. A schematic drawing of MIMO system is illustrated in FIG. 1. As shown in FIG. 1, multiple antennas at the transmit side and receive side constitute multi-antenna wireless channels including space-domain information. Precoding technology is currently one of main technologies for improving data rate by using the space-domain information and pre-processes transmit signal by using channel state information. Precoder is actually a multi-mode beamforming device which matches the transmit signal to channels at the transmit-receive sides. Basic principle of the precoder is separating the transmit signal into a plurality of layers which are orthogonal to each other, making the layers to obtain relatively large gain after passing through channels and maintaining independent orthogonality. Orthogonal and independent data layers transferred between the receive-transmit sides may be M layers at most, which is the minimum number of antennas configured at the both receive side and transmit side. In addition, OFDM (Orthogonal Frequency Division Multiplexing) technology has strong anti-fading capability and high frequency efficiency and is suitable for high speed data transmission in a multi-path scenario and fading scenario. MIMO-OFDM technology which combines MIMO and OFDM technologies has become to a core technique of new generation mobile communication.
For example, 3GPP (the 3rd Generation Partnership Project) organization is an international organization in mobile communication fields and plays an important role in standardization work of 3G cellular communication technologies. 3GPP organization started to design EUTRA (Evolved Universal Mobile Telecommunications System Terrestrial Radio Access) and EUTRAN (Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network) which is also called LTE (Long Term Evolution) project from the latter half in 2004. Downlinks of LTE system adopt the MIMO-OFDM technology. From 3GPP organization Meeting in April 2008 in Shenzhen, China, standardization work of 4G cellular communication system (now called LTE-A system) began to be discussed. During the meeting, a concept “multi-antenna-multi-base-station cooperation” has been widely considered and supported and its basic principle is to provide communication service to one user or more users simultaneously by using a plurality of base stations so as to improve data transmission rate of cell edge users. The precoding scheme in the multi-antenna-multi-base-station cooperation is a key technique for implementing this concept.
However, antenna configurations of multiple cooperative base stations are usually different, resulting that the precoding scheme will face implementation limits and is difficult to realize. In some technical documents, there are three proposals for the inconsistent antenna configuration.
(1) Global Precoding Method
A serving base station and a cooperative base station perform precoding in a centralized manner, i.e., cascading channels from the serving base station and the cooperative base station to a user equipment to form a global channel with large dimensions, and then cascading precoding matrixes of the serving base station and the cooperative base station to form a precoding codeword with a considerable length so as to match the global channel. The centralizedly precoded signal is subject to the global channel and the resulted signal and noise form received signal at the user equipment. The received signal may be expressed with an equation:y=[H1H2 . . . HN]Wx+n. 
In the equation, y is the received signal, x is transmit data, n is noise, N is the total number of the serving base stations and the cooperative base stations, [H1H2 . . . HN] is the global channel from the serving base station and the cooperative base station to the user equipment and W is a precoding matrix for matching the global channel. The core theory of the global precoding method is that the inconsistent antenna configuration does not affect the channel cascading and thus this method is applicable to any antenna scenario. FIG. 2 is a schematic drawing illustrating that three base stations adopt this method. Advantages of this method are large application range and better performance and disadvantages are high complexity of the centralized precoding and large signaling overhead. See Non-Patent Document 1: 3GPP, R1-090585, “Joint Processing Coordinated Multi-point Transmission for LTE-A Downlink”, Texas Instruments.
(2) Distributed Layered Precoding Method
In order to reduce complexity of the above method (1), the multi-antenna-multi-base-station system is considered as a multi-antenna independent base station. Upon that, independent precoding may be performed and independent data layer may be transferred for a single base station, however, orthogonality between the data layers needs to be guaranteed such that the user equipment is able to separate and analyze a plurality of independent data layers. The precoded signal of the distributed-independent-data-layer is channel weighted and combined and the resulted signal and noise form received signal at the user equipment. The received signal may be expressed with an equation:
  y  =                              [                                                                      H                  1                                                                              H                  2                                                            …                                                              H                  N                                                              ]                ⁡                  [                                                                      V                  1                                                            0                                            0                                            0                                                                    0                                                              V                  2                                                            0                                            0                                                                    0                                            0                                            ⋱                                            0                                                                    0                                            0                                            0                                                              V                  N                                                              ]                    ⁢      x        +    n  
In the equation, y is the received signal, x is transmit data, n is noise, N is the total number of the serving base stations and the cooperative base stations, H1, H2, . . . , HN is a channel matrix from the serving base station and the cooperative base station to the user equipment and
         [                                        V            1                                    0                          0                          0                                      0                                      V            2                                    0                          0                                      0                          0                          ⋱                          0                                      0                          0                          0                                      V            N                                ]  is a precoding matrix of the distributed
independent data layer. The core theory of this method is that independent data layers are born on V1, V2, . . , VN respectively, i.e., N base stations transmit independent data layers, and the signal is separated and solved at the user equipment side. The basic idea of this method is to sacrifice cooperative level of multiple stations and solve the inconsistent antenna configuration problem through the independent transmission. FIG. 3 is a schematic drawing illustrating that three base stations adopt this method. An advantage of this method is large application range and disadvantages are that orthogonality between independent data layers is difficult be realized completely and cooperation level of base stations is low, resulting in low system capacity. See Non-Patent Document 1: 3GPP, R1-090585, “Joint Processing Coordinated Multi-point Transmission for LTE-A Downlink”, Texas Instruments.
(3) Antenna Selection Method
This method selects a few antennas from the serving base station and cooperative base station, respectively, to constitute a distributed antenna system, and then uses a single precoding matrix to match channels of the distributed antenna system. From view of the user equipment, channel matrix from the serving base station and cooperative base station to the user equipment is subject to selection and simplified as a virtual channel, i.e., a distributed antenna channel, and then a uniform precoding matrix is used to match the distributed antenna channel, which may be expressed with an equation: y=Wx+n.
In the equation, y is the received signal, x is transmit data, n is noise,  is a distributed antenna channel matrix after antenna selection and W is the precoding matrix used to match the distributed antenna channel. The core theory of this method is to shut down a few base station antennas and reduce channel dimension between multi-base-stations and the user equipment so as to reconstruct a simple channel and perform cooperative communication. FIG. 4 is a schematic drawing illustrating that three base stations adopt this method. An advantage of this method is that implementation is simple and disadvantages are that signaling overhead for antenna selection is large and insufficient antenna diversity will cause worse performance. See Non-Patent Document 2: 3GPP, R1-082847, “On Consideration for CoMP in LTE-A”, ZTE.
In general, the global precoding method (1) adopts the centralized precoding, which obtains better performance but its complexity is high, feedback overhead is large and it is difficult to be realized. The distributed layered precoding method (2) reduces the complexity of implementation, but cooperation level of the base stations is low, system performance is worse and the feedback overhead is still large. Comparatively, the antenna selection method (3) is simplest to be implemented, but its performance is not good.